R1:e3f99947ac80

Fix crumb alignment with new notification layout

Summary: Crumbs misalign because the hit area on the icons was 2px too large.

Test Plan: Test on pages with crumbs. IE, FF, Chrome...

Reviewers: epriestley, btrahan

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D10949